A camera such as an electronic still camera that outputs an object image by using an imaging device such as an electronic imaging device and stores it as a digital image has been mostly used. Recently, electronic imaging devices have been miniaturized and highly integrated, so that even a highly integrated one has been available at a reasonable price. Moreover, since it has been miniaturized by high integration, a lens system installed in a camera using such an electronic imaging device has also been miniaturized.
However, when a zoom lens system is adopted in such a camera, and when a zoom ratio of the zoom lens system is tried to be large, in consideration of aberration correction of each lens group composing the zoom lens system, the number of lenses increases, and the thickness of each lens group becomes large, so that the total lens length also becomes large. Accordingly, although there is a certain limit to miniaturization of a zoom lens system or a camera, recently demand for miniaturization has become higher taking a serious view of design and portability of a camera.
With this background, there has been proposed a method for miniaturizing a zoom lens system by disposing an optical-path-bending element for bending the optical path in the zoom lens system. More specifically, there has been proposed a zoom lens system having a zoom ratio of about three composed of, in order from an object along an optical axis, a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a fourth lens group having positive refractive power, and a prism for bending an optical path being disposed in the first lens group (see Japanese Patent Application Laid-Open No. 2000-131640).
When an optical-path-bending element for bending an optical path is disposed in a zoom lens system, in order to shorten the length of the zoom lens system in the depth direction, in other words, an incident light direction, it is most effective to dispose the optical-path-bending element in the first lens group. In this case, when the optical-path-bending element is made to be compact, the dimension of the zoom lens system in the depth direction can be further smaller.
However, in order to make the zoom lens system become a high zoom ratio, since the total lens length necessary for zooming becomes large, the lens diameter of the first lens group has to be large. Accordingly, the optical-path-bending element has to be large, so that the length in the depth direction cannot be reduced.
Although the conventional zoom lens system has made it possible to shorten the length in the depth direction by disposing an optical-path-bending element in the first lens group, the zoom ratio has been small, and the prism has not been sufficiently small.